COAST's Dr Sally Campbell provides answers to why and how the sea lice that spread from fish

farms cause such damage to the wild salmon population...

Diagram courtesy of Thomas Schram (who retains copyright)

Over the last few months the media has carried articles about sea lice causing the death of young wild salmon, called smolt, as they make their way to sea. In any coastal environment one would expect to find parasitic organisms preying on their hosts and sea lice take their place in natural ecosystems.  Why is it then that sea lice have become such a focus of attention, even to the extent that the collapse of wild salmon stocks in west of Scotland rivers has been linked to sea lice endemic in salmon fish farms on the west coast? Indeed, it is not a problem confined to Scotland; Norway, Ireland, Chile and British Columbia are plagued with sea lice infestations in the overcrowded conditions of fish cages.

Animal husbandry incorporates disease control whether in human groups, farming practices or wild animal populations.  We are dependent collectively on effective control of disease vectors in our society either through containing the carriers of these disease vectors or protecting ourselves from the carriers of disease or infestation. We owe our very survival, lengthening life expectancy and quality of life in our modern society to biologically active chemicals such as antibiotics and anti-viral compounds that we have either isolated from nature or synthesised in drug company laboratories. There is a wealth of knowledge to show that nature uses a vast array of chemical and biological protective mechanisms to combat predators and invasive species.